$\sin(-155^{\circ}) = \text{?}$
To find the sine using the unit circle, first find the angle. Drag the orange point around the circle until $-155^{\circ}$ is selected. The correct angle is selected. Remember, the sine of an angle is represented by the $y$ coordinate of a point on the unit circle. The $y$ coordinate of the point is $-0.423$, so $\sin(-155^{\circ}) = -0.423$.